**1. Introduction**

Until the middle of 1970s, the roles of biochemical engineers had been to design effective processes for production of industrially important proteins and to control bioreactors under optimal conditions. Many microorganisms were isolated from soils, rivers, and seawater, and their genes were randomly disrupted by mutagenic agents such as 1-methyl-3-nitro-1-nitrosoguanidine to enhance the productivity, which was the best procedure of breeding for a long time. Gene manipulation technology born in the late 1870s was a groundbreaking invention, and the technology drastically changed the world of biotechnology. Polymerase chain reaction (PCR) method and genome analysis using high-performance DNA sequencers, which were born after gene manipulation technology, enhanced the drastic progress. Recently, a huge number of genes have been cloned from isolated microorganisms, and many excellent vector plasmids and promoters have been developed.

Recently, the interest of biochemical engineers shifted from breeding using gene manipulation technology to using the discovered novel biocatalysts and the "directed evolution" technology. The idea of directed evolution was proposed by Arnold et al. They proposed that artificial evolution, which is similar to the natural evolution that slowly occurs in the nature world, can be performed at rapid speed using biotechnology. Based on this concept, many studies have been conducted and have become an important target of biochemical engineers. In the future, such artificial proteins will introduce a next wave in the world of biotechnology [1]. Based on this background, I introduce in this chapter the recent advancements in artificial enzymes. There are other important targets for biochemical engineers, and therefore, I recommend referring to other chapters of this book by other authors.
